A lens for improving or protecting one's eyesight is produced in a circular shape, which is commonly called a blank lens. The blank lens should be processed to fit into the frame of an eyeglass for being used. Such processing of the blank lens is carried out by a lens edger which is an apparatus for processing an eyeglass lens. In a prior lens edger, a lens model (i.e., a pattern) which fits into the frame of an eyeglass is used for the blank lens processing. However, recently, a patternless processing apparatus without using the lens model is developed and generally used. The patternless processing apparatus detects the shape of an eyeglass frame or the shape of a processed lens with a tracer, and grinds a blank lens into the detected shape while changing the position of the blank lens according to the detected shape. In the patternless processing apparatus, the blank lens is fixed between two corresponding axes, and the positions of the two axes are changed to grind the blank lens into the desired shape. The patternless processing apparatus not only process the blank lens into a desired shape, but also forms a groove at the edge of the processed lens to fix a lens fixing wire (a groove forming function), grinds the edge of the lens to form a smooth edge (a smooth edge forming function), or forms a -shaped protrusion at the edge of the processed lens which fits into a groove of a eyeglass frame (a -shaped protrusion forming function). FIG. 1 shows a conventional patternless apparatus for processing an eyeglass lens. As shown in FIG. 1, the conventional patternless processing apparatus comprises an opening window 2 for inserting/drawing an eyeglass lens into/from the apparatus and control-switches 3 for controlling the apparatus.
After processing the blank lens into a desired shape, forming a groove at the edge of the processed lens, and grinding the edge with the processing apparatus, if necessary, a drilling operation is carried out for forming a hole on the processed lens. For example, the hole is formed to fix a bridge or a temple on the lens of a rimless eyeglass. For forming the hole, a conventional hand drill or a conventional bench drill is generally used. The conventional hand drill is designed to fit into a human hand, and includes a motor and a chuck for mounting a drill bit. When using the hand drill, power is supplied to the motor to rotate the chuck and the drill bit. The operator holds an eyeglass lens with a hand, and moves the hand drill perpendicularly to the eyeglass lens with other hand to form a hole on the eyeglass lens. In the bench drill, a motor and a chuck for mounting a drill bit constitute a drilling body, and the drilling body is located to move vertically on a bench. The operator positions an eyeglass lens at the trajectory of the drill bit on the bench, and moves the drilling body downwardly to the eyeglass lens to form a hole on the eyeglass lens.
In case of the hand drill, it is dangerous for a non skilled operator to control the hand drill, and it is not easy to form a hole at an exact position. When the hole is formed at a wrong position, the expensive processed lens should be discarded. The bench drill is easy to handle and safer with compared to the hand drill, and more accurate hole formation is possible with the bench drill. However, there is a need for more accurate and safer apparatus for forming the hole on an eyeglass lens.